In the open-end spinning process, the fibers to be spun are first detached from a sliver, separated, and then spun into a yarn in a spinning unit, for example a rotor, or between two friction drums. The opening of a sliver into individual fibers takes place in so-called opening devices. A roller rotates in such an opening device and has spikes or sawteeth on its circumference for combing the fibers out of the sliver. The sliver is drawn from a can or from a sliver bobbin into the opening device by a sliver feed roller. An intake opening guide plate is pressed against the sliver feed roller with a predetermined spring force. The trash contained in the sliver is forced out by the opening roller and for the most part comes detached from the fibers. Because of the relatively high density of the trash particles compared with the fibers, the trash particles gain higher kinetic energy than the fibers, so that in the gap between the opening roller and the housing, they are carried into the radially outer region of the gap between the roller and the housing wall. This circumstance separates the accelerated trash from the fiber stream, by centrifugal force. To that end, a discharge passage is located below the rollers for discharge of trash therethrough into a collecting container or onto a conveyor belt. The trash, which for instance in natural fibers comprises dust, neps, seed and insect residue and the like, is expelled out through this passage and thus leaves the fiber stream moving toward the fiber guide channel.
While dry trash is relatively easy to expel, problems arise with sticky impurities. If the fibers to be spun are cotton fibers, then impurities can still adhere to the cotton fibers, despite the cleaning of the cotton when the sliver is produced. Impurities from insect residue present special problems. This material consists of sticky excretions from insects that attack the cotton, as well as sticky nectar exuded by the plants. This sticky material makes the fibers adherent and thus makes them difficult to separate in the opening unit. Moreover, sticky material deposits form at points of unfavorable flow conditions. Over time, these sticky material deposits accumulate in the direction of the discharge passage and in certain other regions hindering desirable flow conditions. Moreover, additional trash particles and already-separated fibers can stick to these sticky deposits. The fibers catch other fibers and form tufts of fibers. If these tufts then tear loose and get into the spinning apparatus, they result in yarn flaws. Moreover, the accumulation of sticky material requires frequent manual cleaning of the housing.
Disruptions can arise as soon as a sliver contaminated sticky material is drawn in. As a result of the pressure exerted on the sliver in the region of the intake opening, the sticky impurities are pressed with increasing force against the intake opening and continue to stick there. To avoid these phenomena, it is known from DE 40 08 884 A1 for the intake opening guide plate, at least in the region that comes into contact with the fibers of the sliver, to be coated with a surface layer that comprises a metal layer thermochemically applied to the basic material. With the aid of this apparatus, although it is possible to prevent the deposits on the intake opening guide plate, nevertheless the deposit of sticky material inside the opening device, and in particular in the discharge passage, is not prevented by this provision.
It is also known from DE 24 23 241 C3 for the interior of the housing of an opening device for an open-end spinning system to be lined with wear resistant metal foil. Such lining is composed of rolled, thin-walled metal foil that can be adhesively bonded to the interior of the housing. Such lining is intended to provide wear resistance, not to avoid the accumulation of sticky material.
Polytetrafluoroethylene is known from DE-AS 15 60 307 to be used in lining a rotor of an open-end spinning apparatus in order to promote the deposit of fibers in the collecting groove of the rotor during the spinning process. However, such use of polytetrafluoroethylene is not related to preventing the accumulation of sticky material, as trash is assumed to have been expelled by the time fibers enter the rotor.
Accordingly, the need still exists for an improved sliver opening and fiber feeding device which reduces the risk of sticky material accumulations that disturb or interfere with the spinning process.